Fermenting tomato seed in a jam jar and the smell that came with it

12 October 2024 · 3 min read

Tomato seed comes wrapped in a gel that stops it germinating inside the fruit, and the way to get rid of the gel is to let it rot off. That sounds worse than it is, and smells about as bad as it sounds. I squeezed the seeds and pulp from two or three fully ripe fruit of each of five varieties into five small jam jars, added about the same volume of water to each, labeled the lids, and set them on the kitchen windowsill, which was running about 68 °F during the day.

By the second day each jar had a film on top and a smell like a forgotten salad. By the third day the film had become a gray-white fur and the good seeds had sunk to the bottom while the pulp and the hollow seeds floated. That is the signal. I scraped the film off with a spoon, filled the jar with water, swirled, poured off the floating junk, and repeated until the water ran clear and only clean seed remained in the bottom. Each jar took three or four rinses.

Drying was where the first mistake came. I spread the first batch on a paper towel, as seemed obvious, and after two days the seeds were welded to it. Tomato seed is slightly fuzzy and bonds with paper fiber as it dries. I lost about a quarter of that batch tearing them off. The other four went onto coffee filters, which have a smoother surface, and onto a glazed plate for the last day. Both worked. A week on the plate in a warm room and the seeds were dry enough to slide, not stick.

The fifth jar was the cautionary tale. I forgot it behind the dish rack and it fermented for five days instead of three. When I rinsed it out, about a third of the seeds had tiny white roots: the gel was gone, the water was warm, and they had simply started growing. Those are useless for storage and I threw them out, keeping the unsprouted ones, which tested fine. Three days at room temperature is the number, and two in a hot week.

The yield from two or three tomatoes per variety was somewhere between sixty and a hundred and twenty seeds each, which is several years’ worth. Each variety went into a coin envelope labeled with name, year, and the plant it came from. The windowsill has been scrubbed and the household has forgiven me.